It is generally known to color absorptive substrates such as textiles by discrete localized dye application. Generally, such discrete application processes for textiles have evolved along two different approaches. In a first approach (the “drop on demand” approach), a liquid coloring medium such as a dye or liquid colorant is applied directly from valved applicators positioned over the textile substrate to be patterned. In an example of one such system, a valve is opened when the dye or colorant is to be dispensed onto the substrate, and is closed when the requisite quantity of dye has been delivered to the appropriate predetermined area of the substrate.
In one configuration of a “drop on demand” device, a print head containing a plurality of individual dye nozzles is traversed across the path of a substrate to be patterned. One or more dye nozzles may be separately connected to individual dye supplies, each of which may supply dye of a respectively assigned color and provide for multi-color patterning, thereby allowing that applicator to dispense dye of a pre-determined color. Electronically-defined patterning data, in the form of “on-off” instructions, are directed to selected nozzles to dispense dye of the various desired colors onto the substrate as the print head is traversed across the width of the substrate and the substrate is sequentially indexed forward, thereby allowing the dye nozzles comprising the print head to trace a raster pattern across the face of the substrate and dispense dyes of the desired colors on any desired area of the substrate dictated by the selected pattern.
In order to carry out drop on demand application, the dye applicators also may be arranged in a stationary row positioned across the path of the substrate, with applicators for a given color dye being arranged along the length of the row, perhaps intermingled with applicators dispensing dyes of different colors. Alternatively, multiple stationary rows may be used, and the dye applicators for a given color may be restricted to a given row, or may be assigned to different rows. In either case, the pattern control system must provide compensation for the location of the applicators in relation to the substrate. For example, in the multiple-row case, the control system must compensate for the distance between adjacent rows by delaying the patterning instructions for applicators on downstream rows by the time interval necessary for the substrate to travel the distance to these rows. The rows may be arranged in substantially parallel, closely adjacent proximity, aligned substantially transverse to the path of the substrate, or may be arranged in bars that are positioned in some other pre-determined, spaced relation along the path of the substrate to be patterned.
A second approach to discrete dye application is the “recirculating” approach wherein individual dye applicators are associated with a given color. The applicators may be arranged in a fixed orientation relative to a moving textile substrate such as in a series of parallel rows arranged in spaced relation along the path of the moving substrate. However, rather than dispensing dye only when required by the pattern, the applicators in the re-circulating approach are always “on” and thus continuously generate a stream of dye that is directed into a catch basin associated with each row. The dye solution stream can reach the substrate only when it is diverted onto the path of the substrate by an intermittently-actuated (i.e., actuated in accordance with pattern data) transverse stream of air or other control fluid that changes the trajectory of the dye stream and causes the dye stream to avoid the catch basin and strike the surface of the substrate for a time interval sufficient to dispense the quantity of dye specified by the electronically defined pattern data. Separate sets of applicators and corresponding catch basins are used so that dye that is directed into a specific catch basin can be collected and re-circulated to the row of dye applicators assigned to that color dye.
An example of such a device is indicated in FIGS. 1–2, the details of which are discussed below, as well as in a number of U.S. Patents, including commonly-assigned U.S. Pat. Nos. 4,116,626, 5,136,520, 5,142,481, and 5,208,592, the teachings of which are hereby incorporated by reference.
In the devices and techniques described in the above-referenced U.S. patents, the substrate pattern is defined in terms of pixels, and individual colorants, or combinations of colorants, are assigned to each pixel in order to impart the desired color to that corresponding pixel or pixel-sized area on the substrate. The application of such colorants to specific pixels is achieved through the use of many individual dye applicators, mounted along the length of the various color bars (also known as application bars) that are positioned in spaced, parallel relation across the path of the moving substrate to be patterned. Each applicator in a given application bar is supplied with colorant from the same colorant reservoir, with different application bars being supplied from different reservoirs, typically containing different colorants. By generating applicator actuation instructions that accommodate the position of the applicator along the length of the application bar and the position of the application bar relative to the position of the target pixel on the moving substrate, any available colorant from any application bar may be applied to any pixel within the pattern area on the substrate, as may be required by the specific pattern being reproduced.
Regardless of the process by which the dye is dispensed onto the textile substrate surface, various chemical agents sometimes have been applied to the substrate using techniques such as baths, pads, sprayers, or other appropriate devices. Using such devices, surfactants or other dye migration modifying agents have been applied substantially uniformly to the surface of the substrate prior to the patterning step of selectively applying dyes in accordance with pattern information, as is set forth in, for example, commonly-assigned U.S. Pat. Nos. 4,740,214 and 4,808,191 both of which are incorporated by reference as if fully set forth herein.
While the prior practices have been used to provide both uniform and patterned coloration across various substrates, it is believed that the processes of the prior art have not fully realized two desirable capabilities: first, the ability to enhance, selectively and preferentially within a single pattern, the performance of in situ blending within a pattern, and second, the ability to impart, selectively and preferentially within a single pattern, a visual emphasis or sense of three dimensionality or, conversely and concurrently, a visual de-emphasis or sense of two dimensionality.